1. Field of the Invention
The present invention relates to an input device, and, more particularly, to an input device that can be used with a computer or a video screen.
2. Description of the Related Art
An input device can control many systems, for example, an input device can control a menu selection or a character movement in a video game.
As shown in FIG. 3, an input device can include a keytop 2 that is vertically and movably adjacent to a top case 1. An elastic member 3, which is made of an elastic rubber, is disposed below the keytop 2. An end of the elastic member 3 has a dome-shape made of an electrically conductive rubber 4. The electrically conductive rubber 4 has a contact surface 4a that protrudes downward in an arc shape.
A sheet member 5 is disposed below the elastic member 3. A fixed-electrode 6, which is a resistive member, is supported on a portion of a surface of the sheet member 5 opposing the electrically conductive rubber 4. The sheet member 5 is mounted to a surface of a bottom case 7. The keytop 2 is elastically biased upward by a biasing force of the elastic member 3. A gap is formed between the fixed electrode 6 and the electrically conductive rubber 4.
A switching circuit is formed by the electrically conductive rubber 4 and the fixed electrode 6. Through contact between the electrically conductive rubber 4 and the fixed electrode 6, the switching circuit is turned on. When the keytop 2 shown in FIG. 3 is pressed downward, the electrically conductive rubber 4 at an end of the elastic member 3 moves downward towards the fixed electrode 6. This movement causes the electrically conductive rubber 4 to contact the fixed electrode 6, turning on the switching circuit. In addition, the pressing force on the keytop 2 elastically deforms the electrically conductive rubber 4 so that the contact area between the electrically conductive rubber 4 and the fixed electrode 6 changes.
By changing the contact area between the electrically conductive rubber 4 and the fixed electrode 6, the resistance of the fixed electrode 6 changes. This change in resistance can control a menu selection in a personal computer or a character movement in a television game.
It can be difficult manufacture input devices as those described above since the elastic member 3 and the electrically conductive rubber 4 are integrally formed by two molding processes that use a material kneaded with an electrically conductive material and an insulating material, such as rubber. The molding die can also be costly.
An input device embodiment comprises a pressable keytop, an elastic member, a movable electrode, and a fixed electrode. Preferably, the movable electrode can come into electrical conductance with the fixed electrode by an elastic deformation of the elastic member. Preferably, the movable electrode is formed on a sheet member disposed above the fixed electrode. A predetermined gap is provided above the fixed electrode. One of the electrodes comprises an electrically conductive member and the other comprises a resistive member. In one embodiment, the pressing of the keytop forces the movable electrode into contact and electrical conductance with the fixed electrode. The contact creates a resistive change in the resistive member.
In one embodiment, the elastic member has a pushing portion which can push the sheet member into the substantially arc shape pushing surface of the pushing portion. When the movable electrode comes into contact with the fixed electrode, the substantially arc shape of the sheet member is elastically deformed, causing the contact between the movable electrode and the fixed electrode to change.
In a second embodiment, the input device further comprises a base upon which the sheet member can be supported. Preferably, the base is disposed below the sheet member and has a recess of a predetermined depth and/or area. Preferably, the movable electrode is positioned in a portion of the recess and the fixed electrode is positioned on a bottom surface of the recess.
In a third embodiment, the movable electrode is positioned on a first sheet member, a second sheet member is disposed on a surface opposite the movable electrode separated by a predetermined area, and the fixed electrode is positioned on a portion of the second sheet member opposite the movable electrode.